#include <bits/stdc++.h>

using namespace std;

int main()
{
    string s; cin >> s;

    if ((s[0] < '0') || (s[0] > '9') )
    {
        cout << "输入错误：请输入整数！\n";
        return 0;
    }
    
    
    for (auto &&c : s)
    {
        if ((c < '0') || (c > '9') )
        {
            cout << "输入错误：检测到非数字字符！\n";
            return 0;
        }
        
    }

    int a = stoi(s);

    if (a < 0 || a > 100)
    {
        cout << "输入错误：请输入0-100的整数！\n";
        return 0;
    }
    
    if (a < 60)
    {
        cout << "E\n";
    }else if (a < 70)
    {
        cout << "D\n";
    }else if (a < 80)
    {
        cout << "C\n";
    }else if (a < 90)
    {
        cout << "B\n";
    }else
    {
        cout << "A\n";
    }
    
    
    
    
    

    

    return 0;
}

